Common chicory production in aquaponics and in soil fertilized with aquaponic sludge

Abstract

This study assessed the common chicory performance in aquaponics and soil fertilized with aquaponics sludge. The experimental setup consisted of an aquaponic system for farming tilapia (Oreochromis niloticus) and cultivating common chicory (Cichorium intybus), with two interdependent cultivation lines. The aquaponics component consisted of two treatments with six repetitions, comparing the two cultivation methods of (1) floating rafts and (2) substrate. The soil production of the plants consisted of three treatments with three repetitions: (1) fertilization with aquaponic sludge; (2) chemical fertilization (NPK); and (3) control (without fertilization). The sludge (80 L) was collected twice weekly from the bottom of two clarifiers, homogenized, and later applied to the soil. The results of the productive performance and the composition of the plant tissue were evaluated, comparing phyto-technical parameters (NL: number of leaves; LLL: longer leaf length; FM: fresh matter; and DM: Dry matter) of each plant between treatments in the soil and between treatments in aquaponics, and a comparison between cycles for each treatment. Higher yields (g plant−1) were obtained in the aquaponics system with the floating method when compared to the substrate method for the common chicory in the first cycle. In the second cycle, there was a higher yield of vegetables with the substrate method perhaps due to the accumulation of organic matter in the substrate. The vegetables grown in the floating method accumulated higher concentrations of N, P and K in the leaf tissues in both cycles. The production of common chicory in the soil during the first cycle showed no differences between the Sludge and NPK treatments, and both were superior to the Control for all phyto-technical parameters. Differences were shown for the LLL, FM and DM for the second cycle, with higher values shown for plants fertilized with sludge when compared to those treated with NPK or in the Control. These results suggest a cumulative effect of nutrients in the soil after successive sludge applications combined with the mineralization of nutrients, making them available in soil solution. Higher P concentrations in the leaf tissue of the common chicory in the treatment with sludge fertilization suggests higher absorption rates of this element. The aquaponic sludge can be used to fertilize vegetables in the soil and obtain yields similar to and possibly higher than those of mineral fertilization.